Show the entire history of replies above a post when you expend "in reply to"

spec/controllers/posts_controller_spec.rb

@@ -13,7 +13,6 @@ describe PostsController do
   end
 
   describe 'show' do
-
     let(:user) { log_in }
     let(:post) { Fabricate(:post, user: user) }
 
@@ -52,9 +51,26 @@ describe PostsController do
       end
 
     end
-
   end
 
+  describe 'reply_history' do
+    let(:user) { log_in }
+    let(:post) { Fabricate(:post, user: user) }
+
+    it 'ensures the user can see the post' do
+      Guardian.any_instance.expects(:can_see?).with(post).returns(false)
+      xhr :get, :reply_history, id: post.id
+      response.should be_forbidden
+    end
+
+    it 'suceeds' do
+      Post.any_instance.expects(:reply_history)
+      xhr :get, :reply_history, id: post.id
+      response.should be_success
+    end
+  end
+
+
   describe 'versions' do
 
     shared_examples 'posts_controller versions examples' do

spec/models/post_spec.rb

@@ -711,7 +711,6 @@ describe Post do
 
 
   context 'sort_order' do
-
     context 'regular topic' do
 
       let!(:p1) { Fabricate(:post, post_args) }
@@ -722,6 +721,20 @@ describe Post do
         Post.regular_order.should == [p1, p2, p3]
       end
     end
+  end
+
+  context "reply_history" do
+
+    let!(:p1) { Fabricate(:post, post_args) }
+    let!(:p2) { Fabricate(:post, post_args.merge(reply_to_post_number: p1.post_number)) }
+    let!(:p3) { Fabricate(:post, post_args) }
+    let!(:p4) { Fabricate(:post, post_args.merge(reply_to_post_number: p2.post_number)) }
+
+    it "returns the posts in reply to this post" do
+      p4.reply_history.should == [p1, p2]
+      p3.reply_history.should be_blank
+      p2.reply_history.should == [p1]
+    end
 
   end